A team of researchers from Toronto, Canada determined that among US women with early stage breast cancer, the likelihood of diagnosis varies by ethic/racial group. Furthermore, these differences were found to be related with biological differences.

The study entitled “Differences in Breast Cancer Stage at Diagnosis and Cancer-Specific Survival by Race and Ethnicity in the United States”, was recently published the Journal of the American Medical Association.

In this observational study, Javaid Iqbal, M.D., of Women’s College Hospital, Toronto, and colleagues from the University of Toronto, examined a total of 373,563 women with invasive early stage breast cancer. The patients were identified through the Surveillance, Epidemiology, and End Results (SEER) from 18 registries database, between 2004 and 2011.

Data analysis was performed at baseline and at 7 years follow-up of 8 different racial/ethic groups, according to small tumour’s (up to 2cm) biological aggressiveness, such as triple-negative cancers, lymph node metastases, and distant metastases. The primary outcomes of the study were cancer-specific survival, properly adjusted for age at diagnosis, income and estrogen receptor status.

Of the total 373,563 women breast cancer that were analyzed, the results showed that 71.9% were non-hispanic white, 9.4% were hispanic white, 10.4% were black, 6.7% were asian, and 1.6% were of other ethnicities. The median follow-up period was 38 months. Data analysis revealed that compared with non-Hispanic white women diagnosed with stage I breast cancer (50.8%), Japanese women (56.1%) were more likely to be diagnosed and African american women (37.0%) were less likely to be diagnosed.

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Furthermore, the results revealed that at 7 years follow-up, the risk of death from early-stage breast cancer was higher in African american women (6.2%) than in non-Hispanic caucasian women (3%), and even lower in Asian women (1.7%). Additionally, even when adjusting for income and estrogen receptor status, the researchers found that African american women were at higher risk of dying from small-sized tumors (9%) compared to non-Hispanic caucasian women (4.6%).

Findings from this study strongly indicate that the likelihood of diagnosis at an early stage, and survival after diagnosis varies by race and ethnicity. Moreover, these race/ethic differences are related with biological differences such as triple-negative behavior of tumors, lymph node metastasis and distant metastasis.